Rails and Merb are MVC web application frameworks written in and for Ruby. Both the framework is similar in terms of their directory structures and concepts.

Now, We have to compare Rails and Merb. and findout which one is best?

1. Rails is not Modular based. As Merb is Modular.

2. Rails is focused on rapid development for the web programmer. Merb is focused on speed and extensibility.

3. In terms of speed comparison merb is faster than rails. because Merb intentionally is lighter than Rails. Faster means that processing time is spent less inside framework code and more inside the custom code. Merb also uses a faster Ruby re-implementation Erubis over the original and slower ERB.

4. In terms of stability Rails latest version 2.2.2 is very stable and Merb version 1.0. Most of production server uses Rails compare to merb.

5. Rails opinionated in Javascript library, ORM, and template language. Where Merb Javascript library, ORM and template language agnostic.

6. Merb is use Datamapper where Rails more prefer ActiveRecord for database interaction.

7. There are syntax and file structure difference in Rails and Merb.

   a. Create new application ‘test_app’
   Rails: rails test_app
   Merb: merb-gen app test_app
   

   b. Start server
   Rails: script/server
   Merb: merb
   

   c. Interactive console
   Rails: script/console
   Merb: merb -i
   

   d. Generate scaffold
   Rails: script/generate
   Merb: merb-gen
   

   e. Server configuration
   Rails: config/environment.rb
   Merb: config/merb.yml
   

   f. Initialization code
   Rails: config/environment.rb and config/initializers/*
   Merb: config/init.rb

   g. Dependencies
   Rails: config/environment.rb
   Merb: config/dependencies.rb

   h. Response format
   Rails: respond_to
   Merb: provides :xml, :js, :yaml
   

   i. Notice format
   Rails: flash[:notice]
   Merb: message[:notice]
   

   j. Observer
   Rails: before_filter
   Merb: before
   

   k. Set Routes
   Rails: config/routes.rb
   Merb: config/router.rb
   

   l. Migrations
   Rails: db/migrate
   Merb: schema/migrations
   

   M. Testing
   Rails: test Merb: spec & test
   

   So, Based on application requirement you are able to choose which framework is more preferable. Now It’s your time to make decide..

   Great News, that Now Merb gets merged into Rails 3!